Mother of Pearl is

Options

A. Nacre
B. Ostracum
C. Periostracum
D. Both A and B

Answer

**Step-by-Step Solution:**

1. **Understanding the Term "Mother of Pearl":**
- The term "Mother of Pearl" refers to a specific material known as nacre. It is a substance that forms the inner layer of the shells of certain mollusks.

2. **Identifying the Composition:**
- Nacre is an organic-inorganic composite material. This means it is made up of both organic and inorganic components.

3. **Formation in Mollusks:**
- Nacre is produced by certain mollusks as a protective layer. It serves as the inner shell layer, providing strength and protection to the mollusk.

4. **Characteristics of Nacre:**
- Nacre is known for its structural strength and lustrous appearance. This lustrous quality is what gives pearls their shine.

5. **Distinguishing from Other Options:**
- The other options provided (astrakum and periostrakum) are not correct. Astrakum refers to a layer found in some mollusk shells, and periostrakum is the outermost layer of a mollusk shell. Neither of these is synonymous with Mother of Pearl.

6. **Conclusion:**
- Therefore, the correct answer to the question "Mother of Pearl is" is **nacre**.

**Final Answer:**
Mother of Pearl is nacre.

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